Thermally stable jet fuel compositions



FIPSBDB Patented May 8, 1962 3,032,973 THERMALLY STABLE JET FUELCOMPOSITIONS Charles Bedford Biswell, Woodstown, N.J., and Charles N.Winnick, Great Neck, N.Y., assignors to E. I. du Pont de Nemours andCompany, Wilmington, Del., a corporation of Delaware No Drawing. FiledJune 26, 1958, Ser. No. 744,643 3 Claims. (Cl. 60-354) This invention isdirected to improved stabilized jet fuels, particularly to jet fuelscontaining additives to inhibit the deterioration of the fuel underconditions of thermal stress. According to the present invention,improved jet fuels such as grades JP-4 and JP-5 are produced onincorporating therein a metal deactivator and a selected amine salt ofan acid alkyl phosphate.

Specifications governing the formulation of fuels for aircraft turbineengines, ram jet engines and rocket engines are stringent. One of theseis the thermal stability requirement, which may be determined in a CFRfuel coker, a laboratory apparatus designed to measure the hightemperature stability of jet fuels by subjecting the test fuel to thesame level of temperature stress and in a manner similar to thatoccurring in jet engines. In the operation of a jet engine, before thefuel is combusted it is preheated, for example, by the hot operatingengine itself, in which case the fuel, which is pumped through feedlines under pressure, serves as coolant for the engine while on its wayto the combustor. Before entering the combustor, the fuel may attaintemperatures ranging from 300 to 500 F. Under such thermal stress,because of the inherent instability of many of its hydrocarboncomponents, the fuel tends to deteriorate. Varnish-like deposits mayaccumulate in the feed lines, on filter screens, and in feed orificesleading into the combustion chamber, and particles of sludge may becomelodged in the orifices and trapped in the filter systems. Suchaccumulations are harmful, as they may lead to engine malfunctions byrestricting the flow of fuel to combustor, impeding heat transferthrough the metal of the feed lines, and causing imperfect flamepatterns around the orifices when the fuel is ignited.

Tests on commercial JP-4 and JP-S jet fuels in the CPR fuel coker understandard conditions (as described in CRC Manual Number 3, Instructionsfor Operation and Maintenance of CFR Fuel Coker, March 1957, of theCoordinating Research Council, Inc.), have shown that all form some, andmany form rather heavy preheater and filter deposits, which isindicative of the behavior to be expected in the jet engine under fieldconditions.

Various additives have been suggested for improving jet fuel with regardto corrosion of metals and to oxidative deterioration in storage and tosuch deterioration promoted by trace metals. Among these are certainantioxidants of the phenolic and aromatic amine type, corrosioninhibitors, and metal deactivators, which have been approved formilitary use, as described in MIL-J- 5624D, December 24, 1957(superseding MIL-F-5624C, May 18, 1955). The approved additives may beused singly or in combination in specified amounts. None, however, havebeen found in our tests to eifect significant improvements in thethermal stability of the fuel. Some have been found to be harmful, orincompatible with one another in this respect. For example, thewell-known metal deactivator, N,N disalicylidene 1,2 propanediamine,while effective in the approved amounts to reduce tube deposits, isusually harmful to the filterability of the fuel through the heatedfilter system. Also, an approved corrosion inhibitor, which isunderstood to consist essentially of an oil-soluble n-alkyl primaryamine salt of an acid alkyl phosphate, while efiective to improve thefilterability of the fuel (as well as to inhibit corrosion),

is not effective to reduce tube deposits. It might be expected that, incombination, the two would be effective, the one controlling tubedeposits, the other providing filterability. However, such combinationis practically ineffective to reduce tube deposits.

It is an object of this invention to provide jet fuels having improvedthermal stability. In particular, the object of the present invention isto provide significantly improved jet fuels by incorporating into saidfuels the hereinafter described soluble additives of the approvedclasses of metal deactivator and corrosion inhibitor compositions whichfunction compatibly to inhibit the deterioration of the fuel underconditions of thermal stress. These and other objects will becomeapparent in the following description and claims.

More specifically, the present invention relates to a thermallystabilized jet fuel comprising essentially a jet fuel and, as thermalstabilizers therefor, from about 1 to 10 lbs. per 1000 barrels of anN,N-disalicylidene-aliphatic polyamine and from 5 to 50 lbs. per 1000barrels of a jet fuel-soluble salt of (l) a C to C monoamine taken fromthe group consisting of (a) a tertiary alkyl primary amine, (b) asecondary amine whose two organic substituents are monovalent aliphaticor cycloaliphatic hydrocarbon radicals, (c) a tertiary amine whose threeorganic substituents are monovalent aliphatic or cycloaliphatichydrocarbon radicals and (2) mixed monoand dialkyl phosphates whosealkyl groups contain from 8 to 18 carbon atoms.

Furthermore, the present invention is directed to the operation of a jetengine in which the jet fuel to be combusted is in heat-exchangerelationship with the hot engine, in which method of operation the stepof stabilizing the jet fuel against thermal deterioration while in sucha heat-exchange relationship is accomplished by introducing into saidfuel before the fuel enters into said heat-exchange relationship anN,N'-disalicylidene-aliphatic polyamine compound and an amine salt of anacid alkyl phosphate, said amine salt and alkyl phosphates as abovedefined.

This invention is based on the discovery that the described additives,in combination in jet fuel, inhibit the thermal deterioration of thefuel while it is under conditions of thermal stress such as thoseoccurring in a jet engine, and thereby provide for substantially clean,deposit-free flow of fuel from fuel tank to combustor.

As demonstrated in the CFR fuel coker test under thermal conditionssimulating those pertaining in the operation of a jet engine, theadditives of this invention exert an unexpected combined effect tomaintain the flow of fuel through the feed lines and filter system andto inhibit the deposition of sludge and varnish-like deposits in theseparts. It is also significant that these additives impart, to the fuel,properties of anti-corrosion and metal deactivation, as might beexpected, and have no adverse elfect on other properties of the fuelsuch as its waterreaction.

The combined beneficial effect of the subject additives in improving thethermal stability of jet fuel is both unexpected and surprising in viewof the observations that (a) each of the additives alone is onlypartially effective and (b) amine salts of acidalkyl phosphates ingeneral are incompatible with N,N-disalicylidene-l,2,-propanediaminemetal deactivator compositions for the dual purpose of improving thefilterability of the jet fuel and retarding the formation of deposits inthe feed and filter systems under conditions of thermal stress. Theincompatibilty of these two classes of additives is such that thebenefit of reducing tube deposits, normally associated with and to beexpected from the presence in the jet fuel of the metal deactivator, ismarkedly less apparent or is lost altogether.

The amine salts of the acid alkyl phosphates are prepared simply byneutralizing an acid alkyl phosphate or pyrophosphate with theappropriate amine to a pH of about 6-7.

The acid alkyl phosphates and pyrophosphates are obtained by reacting analcohol with phosphoric anhydride (P From about 2 to 4 moles of aprimary alkanol or mixture of such alcohols may be employed per mole ofP 0 Preferred for the present purpose are the ap proximate equimolarmixtures of the monoand dialkyl phosphates produced on using 3 moles ofalcohol per mole Of P205.

For the preparation of the acid alkyl phosphates, the alkanol will be aprimary alkanol, and preferably a branched primary alkanol, having 8 to18 carbon atoms. Examples are the normal alkanols derived from coconutkernel oils. One such fraction, available commercially, consists mainlyof the n-octyl and n-decyl alcohols. Another consists largely ofn-dodecyl alcohol but contains other n-alkanols containing from 10 to 18carbon atoms. Still another ranges from n-C to n-C with n-Cpredominating. Preferably the alcohol will be a mixture of branchedchain primary alkanols, such as those produced in the well-known Oxoprocess from C0, H and a branched chain olefin. Examples of these arethe 0x0 octyl, decyl, tridecyl and octadecyl alcohols, all of which aremixtures consisting predominantly of branched chain primary alkanolsobtained from propylene-butylene dimer, tri-propylene, tetra-propyleneand penta-propylene, respectively.

The amine salts of the subject compositions will be fuel-solublesubstituted ammonium alkyl phosphates prepared by neutralizing an acidalkyl phosphate with a C to C non-aromatic monoamine which broadly maybe a primary amine containing a tert-alkyl substituent on nitrogen, or asecondary or tertiary amine containing monovalent aliphatic orcycloaliphatic hydrocarbyl substituents on nitrogen.

Preferably the amine will be a C to C tert-alkyl primary amine, andpreferably the amine salt will be the salt of such an amine and the acidphosphate derived from the mixed octyl alcohols made by the 0x0 process.Examples of the tert-alkyl amines used to prepare these preferredadditives are: 1,1,3,3-tetramethylbutyl amine (tert. octyl amine); themixed tert. alkyl amine fractions having from 12 to 14 carbon atoms andfrom 18 to 21 carbon atoms, respectively, such as those marketedcommercially under the trade names Primene 81- R and Primene JM-T; andtert. nonyl amine, also available commercially, consisting mainly of theC with small amounts of C and C amines and having a molecular weightrange of 143 to 157.

Representative of the secondary amines and tertiary amines arediisopropylamine, di-Z-ethylhexylamine, N- octenyl-cyclohexylamine,tributylamine, triisooctylamine, and N,N-diethylcyclohexylamine.

Representative substituted ammonium acid alkyl phosphates are describedin the examples. In the preferred embodiment of the invention, therewill be employed the 03-621 tert. alkyl primary amine salts of the mixedmonoand dioctyl phosphates whose octyl groups are derived from the Cbranched primary alkanol mixture produced in the Oxo process.

Produced by neutralization of the mixed monoand dialkyl phosphates to pH6-7, the amine salts consist of two main species which may beschematically represented as follows:

and

ENHO-PqOR 0 OH The metal deactivator component of the subjectcompositions may be prepared by reacting the appropriate o-hydroxyaromatic carbonyl compound with a polyamine having two NH groups, e.g.,1,2-propane diamine and ethylene diamine, as described in US. 2,181,121,2,255,- 597 and 2,813,080. Metal deactivators comprised essentially ofthe reaction products obtained from salicylaldehyde and 1,2-propanediamine are preferred, e.g., N,N- disalicylidene-l,Z- ropanediamine.Others which may be used are derived from mixtures of salicylaldehydeand o-hydroxyacetophenone and 1,2-propane diamine or mixtures of thisdiamine with diethylenetriamine, as described by Bartlett in U.S.2,813,080. As the preferred metal deactivators are derived fromo-hydroxy aromatic aldehydes whose major component is salicyladehyde,they may be regarded as consisting essentially of N,N-disalicylidenecompounds. These metal deactivator compositions, in addition tocontaining the N,N'-disalicylidene compound as the active ingredient,will ordinarily also contain, particularly in their commercial forms,diluents such as xylene or a combination of such a liquid aromatichydrocarbon with a phenol such as xylenol, as described by Bartlett inUS. 2,813,080.

Normally from about 5 to 50 lbs. of an amine salt as defined, and fromabout 1 to 10 lbs. of a metal deactivator as defined will be employedper 100-0 barrels of jet fuel. The actual quantities employed in a givenfuel will depend largely on the susceptibility of that fuel to thermaldeterioration in use. In general, however, about 7.5 to 30 lbs. of anamine salt such as the Primene 81- R salt of the mixed Oxo octylphosphate, and not more than about 2 lbs. of a metal deactivator such asN,N'-disalicylidene-1,2-propane diamine, per 1000 barrels of jet fuel,will be preferred.

The fuel-soluble amine salt and metal deactivator compositions arehomogeneously incorporated into the jet fuel simply by agitating.Preferably these two essential additives are separately added to andblended into the jet fuel to be stabilized. The additives areconveniently handled in liquid form, i.e., as concentrates inhydrocarbon solvents such as kerosene for the amine salt and xylene orxylene-xylenol combination for the metal deactivator.

In addition to containing the metal deactivator and amine s-altcompositions described above, the jet fuel may also contain anantioxidant of the alkyl phenolic or aromatic amine type such as2,6-di-tertiary butyl-p-cresol or N,N'-disecondarybutyl-p-phenylenediamine.

Representative examples illustrating the present invention are asfollows:

PREPARATION OF AMINE SALTS The mixed acidic monoand dialkyl phosphates,and their amine salts described in the examples, were prepared by thefollowing general procedures:

Anhydrous phosphoric pentoxide (P 0 is added gradually under anhydrousconditions to 3 molar equivalents of the alcohol under agitation. Theaddition of P 0 is regulated so as to maintain the reaction temperaturein the range 40 to 90 C. (Good results are ordinarily obtained either at50: 10 C. or at il 0 C.) When the addition of P 0 is complete, thereaction mass is held at 6070 C. for about 12 to 24 hours to completethe reaction (the course of which may be followed by conventionalmethods of analysis for reactants and products). In1 most instances, theacid alkyl phosphate is a viscous o1 The amine salt is obtained byneutralizing the aboveproduced acid alkyl phosphate to a pH of about 7by the addition thereto of approximately 2 moles of amine per mole of P0 originally employed. Conveniently, the amine, together with sufiicientkerosene to produce a final solution containing about 80% of theneutralized salt as the active ingredient, is added gradually to theacid phosphate under agitation, and the reaction mass held at 70:10" C.until it becomes completely homogeneous.

The neutralized salt-kerosene compositions are relatively mobile liquidsat ambient temperatures.

A barrel of jet fuel in the following examples represents 42 U.S.gallons and a specific gravity within the range of 0.739 to 0.845.

TEST METHOD Jet fuels with and without additives, as described below,were tested for thermal stability in the CPR fuel ooker in accordancewith the CRC Manual No. 3 referred to earlier. The fuel coker is alaboratory apparatus designed to measure the fuels high temperaturestability. In principle, it subjects the test fuel to the same level oftemperature stress and in a manner similar to that occurring in jetengines. The unit consists essentially of a fuel system, a preheater anda heated filter section. The preheater, which simulates the hot fuelline sections of the engine, consists essentially of two concentricaluminum tubes, the inner tube housing an electric heater. The heatedfilter section, which is heated electrically and which represents thenozzle area of the engine where fuel degradation particles may becometrapped, contains a sintered stainless steel filter that serves to trapsuch degradation particles forced in the fuel during the test. Theextent of this build up of trapped particles is transmitted as apressure drop across the filter.

In the test, the fuel, at a pressure of 150 p.s.i. and at a fixed flowrate of 6 pounds/hr, enters the preheater through a fuel inlet body andpasses between the inner and outer tu bes where it is heated to therequired temperature by the heater contained in the inner tube. Theheated fuel leaves the preheater through an outlet body where itstemperature is measured by means of a thermocouple. The hot fuel thenenters the heated filter section which also contains a thermocouple formeasuring its temperature. Pressure taps before and after the filtersection lead to a manometer Where the pressure drops across the filteris measured.

In the test runs described below, the fuel presure was 150 pounds andthe fuel flow rate 6 pounds/hr. =For JP-4 fuels the preheatertemperature was 300 or 350 F. and the filter temperature 400 F. For JP-Sfuels the preheater temperature was 400 F., the filter temperature 500The fuel was passed through the unit for 300 minutes or to a pressuredrop of 25 inches of mercury across the filter. If a pressure drop of 25inches occurred before 300 minutes had elapsed, the run was stopped toremove the filter and then continued to 300 minutes.

The pressure drop across the filter and the condition of the preheaterafter 300 minutes with respect to tube deposits is taken as a measure ofthe fuels high temperature stability.

It is standard, in reporting the condition of the preheater tube, torate each inch of its 13 inches of length according to the followingcode:

Tube Deposit Code -no visible deposits l-haze or dulling, no color2barely visible discoloration 3-light tan 4-heavier than 3 As the 3-and4-ratings are apparently the most significant, an abbreviated notationis employed in report ing the present results. The tube deposit ratingsare expressed as follows: the sum of the 13 individual ratings, followedby the total number of 4-ratings, followed by the total number of3-ratings. (The difference between the sum total of the 13 ratings andthe sum of all the 4- and 3-ratings is the sum of the 0-, 1- andZ-ratings.)

EXAMPLE 1 The results tabulated below were obtained in the CFR fuelcoker test described above, on employing a commercial JP-S jet fueldesignated as lot 1 below, with and without the following fuel-solubleadditives: A=the 1,1,3,3-tetramethylbutylamine salt of mixed 1:1

monoand di-Oxo octyl phosphate; concentra- 5 tion= 15 lbs/1000 bbls. offuel.

DMD=N,N'-disalicylidene-1,2-propane diamine; concentration=2 lbs./ 1000bbls. of fuel.

Test Conditions Preheater temp. 400 F. Filter tern 500 F. Fuel pressure150 lbs/sq. in. Fuel flow rate 6 lbs/hr.

[Fuel=.TP-5, lot 1] Deposits Minutes to Test Additives press. drop,

in inches Tube Filter of Hg 1 None 42, 5, 7 Light bronze 40 to 2 A. 33,0, 10 3 MD 14, 0, 0 4 A+DMD 21, 0, 4

25 The data show the instability of the fuel itself, the adverse effectof DMD on filterability, and the marked effect of the combined additivesA and DMD in maintaining fuel flow and inhibiting tube and filterdeposits.

Deposits Minutes to Test Additives piess. drop, 1.11 inches Tube Filterof Hg 5, 0, 0 25,0, 1 do 27, 0, 2 Light bronze.-. 152 to 25 Apparentlylot 2 fuel is itself more stable than the lot 1 fuel of Example 1. Whileeither DMD or B substantially inhibit thermal deterioration of thisfuel, it will be noted that the combination of DMD with B in particular,or with C, provides superior results. Test 10 is for comparison only.The tertiary butyl amine salt, which is excluded from the presentinvention, is actually harmful to filterability in the presence of DMD.This is surprising for in general amine salts of acid alkyl phosv phatescan be relied on to improve filterability.

EXAMPLE 3 Example 2 was repeated, using the fuel of Example 2, 2 lbs./1000 bbls. of DMD and 15 lbs/1000 bbls. of each of the followingfuel-soluble secondary amine salts of mixed monoand dialkyl phosphates:

E=diisopropylammonium OX0 tridecyl phosphate F=di-2-ethylhexylammonium C-C n-alkyl phosphate G=di-2-ethylhexylammonium 0x0 octyl phosphateH=piperidinium 0x0 octyl phosphate I=di-2-ethylhexylammonium n-butyl andisoamyl phos- 7 phate prepared from a 1:1 molar mixture of butyl andisoamyl alcohols J=N-(octeny1)-cyclohexy1ammonium x0 octyl phosphate Theresults of the CRF fuel coker test are tabulated below:

[Fuel=.TP-5, lot 2] Deposits Minutes to Test Additives press. drop,

in inches Tube Filter of Hg ControL. None 29, 3, 2 112 to 25 11 16, 0, 0300 to 0.1 32, 0, 9 300 to 0.5 21, 0, 3 do 300 to 0.0 31, 2, 3 Darkbronze 190 to 25 29, 0, 2 None 214 to 25 5, 0, 0 Light bronze... 300 to0.13

Tests 14 and 15 are for comparison only, amine salts H and I beingoutside the scope of the invention for reasons of inoperability. Aminesalt F appears to be marginally effective in reducing tube deposits,though it greatly aids filterability. Comparison of test 12 with test 13(and with tests 11 and 16) explains the preference for the branchedprimary alkyl groups in the phosphate; test 14, however, shows that thisfeature alone is not enough to provide the desired results.

EXAMPLE 4 The following results were obtained, using the fuel of Example2, 2 lbs/1000 bbls. of DMD and 15 lbs./ 1000 bbls. of each of thefollowing fuel-soluble tertiary amine salts of mixed 1:1 Oxo octylphosphate:

K=tributylamine salt L=N-diethylcyclohexylamine salt M=triisooctylarninesalt [Fuel=JP-5, lot 2] Deposits Minutes to Test Additives press. drop,

in inches Tube Filter of Hg K-j-DMD..- 31, 0, 6. Very light bronze..-300 to 0.15 L+DMD None 300 to 1.57 M+DMD 12, 0, 3---. do 300 to 0.00

For the control run see Example 2.

EXAMPLE 5 The J-P-S jet fuel of Example 1 was treated to contain 2lbs/1000 bbls. of DMD and lbs/1000 bbls. of each of the following aminesalts of the mixed 1:1 Oxo octyl phosphate, or of commercial additive Q:

B=the Primene 81-R salt K=tributylamine salt M=triisooctylamine saltN=2-ethylhexylamine Q=a commercial corrosion inhibitor, believed to bethe cocoamine salt of acid C -C alkyl phosphates [Fuel=JP-5, lot 1]Deposits Minutes to Test Additives press. drop,

in inches Tube Filter of Hg Control 1-- None 42, 5, 7.-.- Light br0nze10 to 25 M d0... 29 to 25 0 0.1 .05 0.0 0.0 0.0 Light brown 0. 0

The over-all effectiveness of the subject additives of tests -22 issurprising in view of the relative ineffectiveness of the excludedadditives of tests 23 and 25 to inhibit deposit formation.

EXAMPLE 6 The JP-S of Example 1 was treated to contain DMD andfuel-soluble additives A of Example 1, K of Example 5, N of example 5,and P, the tert. nonlyamine salt of the mixed 1:1 monoand di-Oxo octylphosphate, in the quantities given below.

Each of the fuel samples was then aged in the dark for 6 weeks at 110 F.in 5 gallon metal cans before it was run in the CFR fuel coker test. Thefuel coker test re sults for the aged fuels follow:

Cone. Deposits Minutes to Test Additives lbs/1000 press. drop,

bbls. in inches Tube Filter of Hg 26 None 42, 6, 4 Light bronze- 29. 5to 25 27 A+DMD 7. 5+2 17, 0, 0 300 to 0.0 28 A+DM 15+1 8, 0,0 300 to 0.029 K+DMD 30+2 31, 0, 6 300 to 0.08 30 P+DMD 7. 5+2 13, 0, 0 300 to 0.0831"- P+DMD l5+2 ll, 0, O 300 to 0.1 32 P+Dl\1D 30+2 27, 0, 3 d0 300 to0. 0 33 N+DM 7. 5+2 37, 3, 7 Light brown" 300 to 0.1 34 N+DMD 15-l-2 32,2, 3 None 300 to 0.0

Tests 33 and 34 are for comparison. Additive N, the Z-ethylhexylaminesalt, is excluded from the scope of the invention. The compatibility ofthe subject additives with DMD in fuel under accelerated storageconditions is noteworthy.

EXAMPLE 7 Example 6 was repeated on the JP-S fuel of Example 1, with andwithout the combined additives DMD and A of Example 1. The followingresults were obtained in the fuel coker test after the treated fuelsamples were aged in the dark for 12 weeks at 110 F. in 5 gallon metalcans.

Substantially the same relative order of results are obtained in the CFRfuel coker test with commercial JP-4 jet fuels, as described in theabove examples for the JP-S fuels. The combined effect of the amine saltas defined and a metal deactivator such as N.N-disalicy1idene-l,2-propane diamine, is to improve the filterability of the fuel and lessentube and filter deposits.

None of the additives, in any of the fuel compositions described above,promoted the emulsification of water in the fuel. All fuel compositionspassed the standard water tolerance test, involving the use of waterbuffered with phosphates to pH 7, as described in Method 3251 of FederalSpecification VV'L-79 1e.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that this invention is not limited to the specificembodiments thereof except as defined in the appended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A thermally stabilized jet fuel, consisting essentially of a liquidhydrocarbon jet fuel, and, as thermal stabilizers thereof, from about 1to 10 lbs. per bbls. of said fuel of an N,N-disalicylidene aliphaticpolyamine and from about 5 to 50 lbs. per 1000 bbls. of a jetfuel-soluble salt of (1) a C -C monoamine taken from the groupconsisting of (a) a tertiary alkyl primary amine, (b) a secondary aminewhose two organic substituents are monovalent saturated hydrocarbonradicals, (c) a tertiary amine whose three organic substituents aremonovalent saturated hydrocarbon radicals, and, (2) mixed monoanddialkyl phosphates whose alkyl groups contain from 8 to 18 carbon atoms.

2. The thermally stabilized jet fuel of claim 1 wherein the amine saltadditive is a C3-C21 tertiary alkyl primary amine salt of an acid alkylphosphate, the alkyl groups being branched chain alkyl groups havingfrom 8 to 18 carbon atoms.

3. An improved method of operating a jet engine wherein the jet fuel tobe combusted is in heat-exchange relationship with the hot engine whichcomprises the step of combusting a liquid hydrocarbon jet fuelstabilized against thermal deterioration by introducing into said fuel,before the fuel enters into said heat-exchange relationship, anN.N-disalicylidene aliphatic polyamine, and, a jet fuelsoluble salt of(1) a C5-C24 monoamine taken from the group consisting of (a) a tertiaryalkyl primary amine,

(b) a secondary amine whose two organic substituents are monovalentsaturated hydrocarbon radicals, (c) a tertiary amine whose three organicsubstituents are monovalent saturated hydrocarbon radicals, and, (2)mixed monoand dialkyl phosphates whose alkyl groups contain from 8 to 18carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS2,282,513 Downing et a1 May 12, 1942 2,297,114 Thompson Sept. 29, 19422,602,049 Smith et al July 1, 1952 2,768,884 Bowers Oct. 30, 1956FOREIGN PATENTS 79l,398 Great Britain Mar. 5, 1958

1. A THERMALLY STABILIZED JET FUEL, CONSISTING ESSENTIALLY OF A LIQUIDHYDROCARBON JET FUEL, AND AS THERMAL STABILIZERS THEREOF, FROM ABOUT 1TO 10 LBS. PER 100 LBBLS. OF SAID FUEL OF AN N,N''-DISALICYLIDENEALIPHATIC POLAMINE AND FROM ABOUT 5 TO 50 LBS. PER 1000 BBLS. OF A JETFUEL-SOLUBLE SALT OF (1) A C6-C24 MONOAMINE TAKEN FROM THE GROUPCONSISTING OF (A) A TERTIARY ALKYL PRIMARY AMINE, (B) A SECONDARY AMINEWHOSE TWO ORGANIC SUBSTITUENTS ARE MONOVALENT SATURATED HYDROCARBONRADICALS, (C) A TERTIARY AMINE WHOSE THREE ORGANIC SUBSTITUENTS AREMONOVALENT SATURATED HYDROCARBON RADICALS, AND, (2) MIXED MONOANDDIALKYL PHOSPHATES WHOSE ALKYL GROUPS CONTAIN FROM 8 TO 18 CARBON ATOMS.